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Anatomy of the Eye
Anatomy of the Eye

The eye has been called the most complex organ in the body. It's amazing that something so small can have so many working parts. But when you consider how difficult the task of providing vision really is, perhaps it's no wonder after all.

The eye is like a camera. It lets light in through the cornea, which is like a camera's opening. The amount of light allowed in is controlled by the pupil, which opens and closes a bit like a shutter. The light focuses on the retina, which sends the image to the brain, acting as film would in order to record the light (the photo itself).

Other eye structures support the main activity of sight. Some carry fluids - tears and blood - to lubricate or nourish the eye. Others are muscles that allow the eye to move. Some protect the eye from injury - lids and the epithelium of the cornea. And some are messengers, sending sensory information to the brain - pain-sensing nerves in the cornea and the optic nerve behind the retina.

Computer Vision Syndrome
Irritated Eyes

Computer Glasses

Many computer users need a pair of glasses for their computer work that is different from the glasses they use for their other common visual needs. They either have a different prescription or a different lens design from their usual glasses.

In other cases, the computer user may have a vision disorder that would not otherwise require correction if they weren't performing a demanding visual job such as at the computer. In these cases, the person needs a pair of glasses that they would not need if they weren't working at a computer. These are called "computer glasses".

Bifocals or progressive addition lenses that are usually prescribed for presbyopia don't work well for computer work. The best solution for the presbyopic computer user is a lens which is specifically designed for the ergonomics of the computer workstation.

These special computer lenses are designed to accommodate the unique viewing distances and angles at a computer and work for presbyopic computer users and can also work for others who require lenses for their computer.

Talk to your eye doctor to determine if you need computer glasses.

Irritated Eyes

Symptoms such as dry eyes, irritated eyes, contact lens problems, or if blinking helps to clear your vision can be due to dry eyes. It is common for computer users to have dry eyes. This is because we don't blink much and we hold our eyes wide open when working at the computer.

The following steps can help alleviate your symptoms:

  • Use artificial tears to re-wet and lubricate your eyes. Use as recommended by either your doctor or the manufacturer.
  • Lower your computer screen so that the center of the screen is 4-8 inches below your eyes.
  • If you are seated in a draft or near an air vent, try to eliminate the flow of air past your eyes.
  • Low humidity or fumes aggravate a dry eye condition. If you have these conditions in your work place, fix them if possible.
  • Concentrate on blinking whenever you begin to sense symptoms of dry or irritated eyes.
  • Every once in a while (especially when you sense the symptoms) close your eyes and roll them behind your closed eye lids.

If symptoms persist you should consult your eye doctor for immediate help.

Lighting Problems

A very common reason for discomfort glare being a problem for computer workers is lighting. Light often leaves the overhead fluorescent fixture in a wide angle, resulting in light directly entering the eyes of the workers.

Good lighting design can significantly help reduce discomfort glare. Light leaving the fixture can be directed so that it goes straight down and not into the eyes of the room occupants. This is most commonly accomplished with the louvers in the luminaire or fixture. An even better solution is indirect lighting in which the light is bounced off the ceiling - resulting in a large low luminance source of light for the room.

One way to test for glare discomfort is to have the worker look at their computer screen and be aware of any bright lights in their peripheral vision. They the can use their hand to shield their eyes like a baseball cap visor and note whether they sense an immediate improvement in their comfort. They should try this 2-3 times. If they notice an immediate sense of improved comfort by eliminating the lights from their peripheral vision, then they are experiencing glare discomfort.

Solutions to glare discomfort

If bright lights are deemed to be contributing to discomfort, then they should be removed or mitigated in some manner. There are several ways in which they can be improved.

  • Turn off some of the offending fluorescent lights. Sometimes it is a single fluorescent fixture in the ceiling which is just in front of the person. Very often a single offending fixture can be turned off without creating lighting deficiencies.
  • Fluorescent light fixtures can be retrofit with parabolic louvers which direct the light straight down into the room. The parabolic louver (the louver is the egg crate-like cover that directs light into the room) directs the light from the fluorescent tubes straight downward, hence it is not directed into anyone's eyes.
  • Re-orient the work station so that bright lights are not in the field of view. Sometimes the work desk can be rotated 90 or 180 degrees so that the fluorescent lights or bright windows are not in the field of view.
  • Wear a visor. This is actually a very efficient way to eliminate the brightness of overhead fixtures. A person can wear a visor for a day or two as a test to determine the extent to which the light problem alleviates discomfort at the end of the day.
  • Avoid bright reflective surfaces. In some work environments, the desk tops are white. This results in the desk top surface becoming a discomfort glare source. Desktops and other furnishings should have a matte, medium reflective surface.
  • Use blinds or drapes on windows. This is often the most difficult to implement because people like the views out of windows. However, if the view out the window is considerably brighter than the objects in the room (as it almost always is) then the window is serving as a discomfort glare source.
  • Evaluate whether auxiliary lighting (for example a desk lamp) on reference documents is causing glare discomfort.
  • Change the brightness of the screen. The brightness of the screen should be adjusted to match the brightness of the visual objects which immediately surround it.
  • Hang or erect partitions. Very often the offending light sources can be eliminated from the field of view by erecting or moving partitions.
Conditions and Diseases
Age-Related Macular Degeneration (AMD)

AMD is a common eye disease associated with aging that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving. In some people, AMD advances so slowly that it will have little effect on their vision as they age. But in others, the disease progresses faster and may lead to a loss of vision in one or both eyes.

Types

AMD occurs in two forms. Wet (vascular) and dry (atrophic). Although only ten percent of all people with AMD have wet AMD, it is responsible for the vast majority of severe, AMD-related vision losses. As dry AMD worsens, new blood vessels may begin to grow and cause wet AMD. Because these new blood vessels tend to be very fragile, they will often leak blood and fluid under the macula. This causes rapid damage to the macula that can lead to the loss of central vision in a short period of time.

Dry AMD affects the other ninety percent of cases. The earliest sign of dry AMD is the development of waste material deposits, called drusen, that appear as tiny orange or yellow dots among the retinal pigment epithelial cells. These deposits are initially tiny and few in number, but they may grow larger and become more numerous. Scientists are still not sure what causes dry AMD. Studies suggest that an area of the retina becomes diseased, leading to the slow breakdown of the light-sensing cells in the macula and a gradual loss of central vision.

Causes

Most cases of macular degeneration are age-related, meaning older people are more likely to have it. Risk factors include: being white or female, having a family member with AMD, smoking, high blood pressure, farsightedness and obesity. The exact causes are still unknown. Because the condition often runs in families, AMD may be hereditary.

Symptoms

The main symptom is central vision loss, which is gradual in dry AMD and sudden in wet AMD. Other symptoms include blurry or fuzzy vision, dark spots in the center of vision, difficulty reading or performing detail work; and seeing straight lines as wavy or bent.

Treatments

No treatment currently exists for dry AMD. It has been suggested that taking certain extra vitamins and minerals may slow the progress of the disease. But this treatment needs much more research before scientists can know for sure if it's helpful.

There are two FDA approved treatments available for wet macular degeneration: photocoagulation and photodynamic therapy.

Surgeons use laser photocoagulation to treat leakage that results from wet AMD. The laser beam burns abnormal blood vessels to seal the leakage. By slowing or stopping the leakage, the progression of macular degeneration is also slowed or stopped. Only about one-tenth of patients with wet AMD are candidates for this procedure.

Photodynamic therapy (PDT) is a minimally invasive outpatient procedure. The procedure involves a light-activated drug and low-intensity, or non-thermal, laser light. The eye is numbed with eye drops and a special contact lens is placed on the eye. The light-activated drug is then administered intravenously. The laser light is directed through the contact lens to the affected area of the retina and closes up leaky blood vessels. Patients may require recurrent treatments as often as every 3 months for the first year. After the first year, treatment is required less frequently.

Symptoms

The main symptom is central vision loss, which is gradual in dry AMD and sudden in wet AMD. Other symptoms include blurry or fuzzy vision, dark spots in the center of vision, difficulty reading or performing detail work; and seeing straight lines as wavy or bent.

Treatments

No treatment currently exists for dry AMD. It has been suggested that taking certain extra vitamins and minerals may slow the progress of the disease. But this treatment needs much more research before scientists can know for sure if it's helpful.

There are two FDA approved treatments available for wet macular degeneration: photocoagulation and photodynamic therapy.

Surgeons use laser photocoagulation to treat leakage that results from wet AMD. The laser beam burns abnormal blood vessels to seal the leakage. By slowing or stopping the leakage, the progression of macular degeneration is also slowed or stopped. Only about one-tenth of patients with wet AMD are candidates for this procedure.

Photodynamic therapy (PDT) is a minimally invasive outpatient procedure. The procedure involves a light-activated drug and low-intensity, or non-thermal, laser light. The eye is numbed with eye drops and a special contact lens is placed on the eye. The light-activated drug is then administered intravenously. The laser light is directed through the contact lens to the affected area of the retina and closes up leaky blood vessels. Patients may require recurrent treatments as often as every 3 months for the first year. After the first year, treatment is required less frequently.

Glaucoma

Glaucoma is a leading cause of blindness. Over 2.2 million Americans have already been diagnosed with glaucoma, and 100,000 new cases are diagnosed each year. Worldwide, there are an estimated 65 million cases of glaucoma. About 2% of people between the ages of 40 and 50, and 8% of those over 70, have elevated intraocular pressure in one or both eyes.

Glaucoma is often called the "silent thief of sight" because there are no early warning signs. It's estimated that more than two million people may have the disease and not know it.

There are 120,000 people in the United States who are blind as a result of glaucoma, which accounts for 9-12% of all cases of blindness. It is the second leading cause of permanent vision loss and the leading cause of preventable blindness. Open angle glaucoma accounts for 19% of blindness in African Americans and 6% in Caucasians. Glaucoma is six to eight times more common in African Americans than Caucasians, and they are more likely to become blind from it.

Glaucoma is caused by increased intraocular pressure (IOP) resulting either from a malformation or malfunction of the eye's drainage structure. The eye constantly produces aqueous, the clear fluid that fills the anterior chamber, which is the space between the cornea and iris. The aqueous filters out of the anterior chamber through a complex drainage system. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision. However, early detection and treatment can slow, or even halt the progression of the disease.

Types

There are many different types of glaucoma but the two major types are primary open-angle and angle- closure.

Primary open-angle glaucoma accounts for 60-70% of glaucoma cases in the United States. In open-angle glaucoma, the aqueous humor is unable to drain out of the eye, damaging the optic nerve. Most people do not experience symptoms until their vision is compromised and extensive damage to the optic nerve has been done. Peripheral vision is affected before central vision.

Angle-closure glaucoma, also known as narrow-angle glaucoma, accounts for fewer than 10% of cases. In most cases, the iris blocks the trabecular meshwork, preventing drainage of aqueous humor and raising intraocular pressure. If the drainage channel is completely blocked, IOP rises suddenly, causing acute angle-closure glaucoma. Symptoms may be severe and include extreme eye pain, nausea, blurred vision, and halos around lights. Acute angle-closure glaucoma is a medical emergency that must be treated by an ophthalmologist immediately. Permanent vision loss can occur within days.

Symptoms

Detection and prevention are only possible with routine eye examinations. However, certain types of glaucoma, such as angle closure and congenital, do cause symptoms. Among these are a sudden decrease in vision, severe eye pain, headaches and sensitivity to light, sudden increase in IOP and swollen or clouded cornea.

Because glaucoma does not cause symptoms in most cases, those who are 40 or older should have an annual examination including a measurement of the intraocular pressure.

Treatment

Most patients with glaucoma require only medication to control the eye pressure. Sometimes, several medications that complement each other are necessary to reduce the pressure adequately.

Surgery is indicated when medical treatment fails to lower the pressure satisfactorily. There are several types of procedures. Some involve lasers and can be done in the office; others must be performed in the operating room. The objective of any glaucoma operation is to allow fluid to drain from the eye more efficiently.

Laser surgery is recommended for those who have not experienced favorable results from medication. A laser is used to make a small opening in the eye to drain fluid. There are different types of laser surgery and the choice is based on the type of glaucoma and the health of the eye. In narrow-angle glaucoma, a YAG laser is used to make a small opening in the eye to drain fluid. Laser surgery is usually done on an outpatient basis.

Diabetic Retinopathy

Diabetic retinopathy is a leading cause of blindness in the United States, occurring in about 25/50% of people with diabetes.

People with Type 1 diabetes are especially at risk for retinopathy. When Type 1 diabetes coexists with hypertension, a person may be four times as likely to develop proliferative retinopathy, the most damaging form of diabetic retinopathy. It occurs in about 60% of people with Type I diabetes and in about 5% of people with Type II diabetes within about two decades after diabetes is diagnosed.

When diagnosed early in the course of the disease, diabetic retinopathy can be effectively managed. Annual eye examinations are essential in diabetic care to prevent permanently impaired or lost vision.

Vision defects accompanying Type I diabetes are somewhat common, and can lead to blindness without prompt and ongoing intervention. Diabetic retinopathy that can cause vision loss occurs with damage to the retina where light-sensitive cells are located and images are processed.

Signs and Symptoms

In its earliest stages, diabetic retinopathy usually does not produce symptoms. Once macular edema develops, vision blurs and the quality of vision may fluctuate.

Bleeding can also cause vision loss, as the disease advances. As bleeding and leakage increase, vision decreases. In severe cases, vision is so impaired that the patient is only able to distinguish light from dark in the affected eye.

Treatment

Diabetic retinopathy can be treated with laser photocoagulation to seal off leaking blood vessels and destroy new growth. Another procedure called a vitrectomy removes blood that has leaked into the vitreous humor. Lost vitreous humor is gradually replaced by the body, and vision improves.

 

Spots and Floaters

Spots called floaters are small, semi-transparent or cloudy specks or particles within the vitreous, the clear, jelly-like fluid that fills the inside of your eyes. They appear as specks of various shapes and sizes, threadlike strands or cobwebs. Since they are within your eyes, they move as your eyes move and seem to dart away when you try to look at them directly.

Spots are often caused by small flecks of protein or other matter trapped during the formation of your eyes before birth. They can also result from deterioration of the vitreous fluid, due to aging; or from certain eye diseases or injuries.

Most spots are not harmful and rarely limit vision and many fade over time. However, suddenly seeing new floaters, or floaters accompanied by flashes of light or peripheral vision loss, may indicate a retinal detachment. You should see your eye doctor for a comprehensive examination when you notice sudden changes or see increases in them to determine if what you are seeing is harmless or are symptoms of a more serious problem that requires treatment.

Children's Frames

Children's eyewear, like children themselves, has become more sophisticated.

Kids want their glasses to be just like those worn by their tween, teen, and adult friends and family. Want to know what frames kids crave? Hit the mall and check out what teens are wearing. According to many dispensers, children view teenagers as the reference point for what's cool. Kids want whatever teenagers are wearing. And name brands are important to them. One way to ensure that kids will love their new eyewear is to use color and face shape analysis when helping select their frames.

Grownups want their children's eyewear to be safe, durable, and affordable. Frame manufacturers are addressing kids' needs through the use of more subtle colors and shapes. And they're making mom and dad content by using durable materials and spring hinges, yet keeping the cost of eyewear down.

Kids look at fashion as an important part of who they are, and that of course spills over into the eyewear they choose. Two trends that have been emerging in adult frames recently have also become prominent in the youth market. Colors are getting more daring, and temples are featuring more details such as laminations, laser etching, and embellishments.

The color palette of kids' eyewear stretches across a wider range than ever before. Brighter, as well as more interesting tones, are becoming more apparent in kids' eyewear.

Regardless of the age group, today's eyewear for the younger set is definitely branching out and getting away from classic "kid styling." The hottest trends in eyewear for kids and teens include novel interpretations of hip adult fashions.

Boys vs. Girls

For the most part, young boys gravitate toward metals and the girls love the new plastics especially the laminates. While the preference for frame finishes might be divided between boys and girls, many opticians note that kids of both genders want frames that make a statement in color. Another trend opticians have noticed is the growing demand for geometric shapes in kids' frames. The rectangular styles are the most popular.

Handling and Care

Children are tough on eyeglasses and a good warrantee is a value-added feature. If the parents wear eyeglasses, they probably understand quality and will be willing to pay for it for their child, especially if that translates into longer wear and low maintenance.

Be sure to train kids in how to use and care for the eyewear. Discuss how to properly remove eyeglasses using two hands, how to clean them, how to put them on, how to put them in the case, and when to seek help if the eyewear doesn't fit or function properly. The time spent adds greatly to the successful wearing of the eyewear and enhances the experience.

The Key Role of Nutrition in Eye Health

There has been a lot of interest in the role of nutrition and nutritional supplements, such as vitamin tablets, and their effect on vision. The main focus has been on how vitamins and minerals might affect age-related eye condition such as age-related macular-degeneration and cataracts.

The Importance of Good Nutrition

Good nutrition is very important for both your general and eye health. Good nutrition helps our body to grow, repair wear and tear, protect against infection and to function properly. An eye condition called ?xerophthalmia', which is a common cause of childhood blindness in developing countries, is a good example of how nutrition and eye health go hand in hand. This condition is caused by a lack of vitamin A in a person's diet and could be prevented by eating fresh vegetables, fat (animal and plant) and protein such as meat, eggs, cheese, fish, poultry, milk, yogurt, dairy products, grains, etc.

A good diet, full of fresh fruits and vegetables, may help protect against macular degeneration in later life. Some studies have shown that a good diet can help in preventing AMD and age-related cataracts.

Vitamins and the eye

Vitamins, which contain antioxidants, have been linked with eye health in various studies and clinical trials. They help to maintain healthy cells and tissues in the eye.

The main focus has been on the antioxidant vitamins A, C and E. These vitamins can be found in many different sources of fruit and vegetables such as oranges, kiwis, dried apricots, green leafy vegetables, tomatoes, peppers, carrots, spinach. They can also be found in nuts, seeds, dairy products and eggs. These are only a few of the food types in which antioxidant vitamins can be found.

Lutein and Eye Health      

More recently it has been suggested that two types of antioxidants, known as carotenoids, called Lutein and Zeaxanthin may also help with eye health. Lutein and Zeaxanthin can be found naturally in vegetables and fruit. For example, Lutein can be found in yellow peppers, mango, bilberries and green leafy vegetables such as Kale, spinach, chard and broccoli. Zeaxanthin can be found in orange sweet peppers, broccoli, corn, lettuce (not iceberg), spinach, tangerines, oranges and eggs. Many of these overlap with food types in which vitamins A, E and C are present.

As a result of various research projects into carotenoids such as Lutein and Zeaxanthin, there are now many different vitamin supplements for eye health on the market. They usually contain the daily-recommended amount of the vitamins and minerals found to be of benefit for eye health.

Evidence regarding the benefits of nutritional supplements against eye disease is conflicting and there is no real agreement among researchers on this subject. However, it's now well-known that a healthy, balance diet full of fresh fruits and vegetables is good for the health of your eyes.

Remember these key points for healthy eyes:

  • Eat a good, balanced diet with lots of fresh fruit and vegetables
  • Discuss how to improve your eye health with your eye doctor
  • Get your eyes tested at least every two years and more frequently.

 

Clearing Up the Meaning of 20/20 Vision

With all of the complicated terms associated with vision, from prescription coordinates to the myriad of eye condition terms, one might think that "20/20 Vision" would have a far more complicated meaning than it does. In fact, you may be surprised just how simple the basis for 20/20 vision is.

When a patient takes a basic "eye chart" vision test in their eye doctor's office, they are undergoing what is referred to as a visual acuity test. This test utilizes a "Snellen chart," which you may know as that white chart with progressively smaller lines of letters moving down the chart. From twenty feet away, with one eye covered, the patient reads aloud the line with the smallest text they can see clearly. This is repeated with the other eye covered. Results usually determine whether or not a patient may need corrective lenses to improve their vision.

While 20/20 vision refers to "normal" quality eyesight, what 20/20 actually means is this: At 20 feet from the chart, a person with "normal" vision can read the smallest line of text with one eye closed. Therefore, that person can see at 20 feet away what a person with "normal" vision can also see clearly from 20 feet away. Someone with 20/40 vision must be no more than 20 feet away to clearly see what a person with 20/20 vision can see from 40 feet. This measurement scale continues upward in 20-foot increments to such distances as 20/200, which is considered legally blind.

As much as the term 20/20 has become synonymous with "perfect" vision, this is simply not the case. There are many people who sport 20/15 vision. 20/15 vision means that individual can see objects clearly from 20 feet away that people with "normal" vision need to be 15 feet away to see. There are also vision researchers developing vision technology that can reportedly improve an individual's vision to somewhere in the range of 20/5. There are differing opinions in the optical world as to how practical this level of vision would be to the general public.

Whatever your visual acuity, hopefully, this information helps clear up any confusion you may have about the term "20/20 vision." If you have questions that have not been answered here, consult your eye doctor.

 

Eye Exams: Your Windows to Wellness

Eye exams can reveal a lot about your health.

Sometimes a routine eye exam ends up being not so routine after all. Charles Brownlow, O.D., a practicing optometrist for 27 years and executive vice president of the Wisconsin Optometric Association, remembers one such exam a few years ago.

"I'd been seeing this particular patient -- let's call him 'Joe' -- for about 15 years," says Dr. Brownlow, "and one morning he came in for his regular eye exam.

"At first everything seemed strictly routine. Joe's vision hadn't changed in two years, and his eyes looked perfectly normal.

"But when I asked him some questions about his vision, he explained that one eye felt weaker than the other. He told me: 'Doc, things just don't look as bright or as sharp out of that eye!'

"After reviewing his chart and listening to his symptoms, I knew something was wrong and that we had to take action," recalls Dr. Brownlow. "Thankfully, my education and experience paid off that day. Countless other patients have also benefited over the years when visiting an optometrist because they believe they have a routine vision problem, but leave the office with a far different diagnosis."

Dr. Brownlow moved quickly. He referred his patient to a general physician, who sent him to a specialist. The diagnosis: carotid artery disease, in which fatty deposits build up on artery walls where they can trigger fatal blood clots.

"Joe had a major blockage in the carotid artery on one side of his neck," says Dr. Brownlow, and the blockage was cutting down on the blood supply to the brain and eye. "They hurried him into surgery, and he managed to avoid what could have been a life-threatening stroke."

Regular Eye Exams Are the Key

Most eye exams don't produce such dramatic consequences, but there's no doubt that getting your eyes checked every year or two is a key step in protecting the priceless asset that is your vision.

"Regular eye exams are extremely important, because they can uncover major health problems such as diabetes and high blood pressure," says Dr. Brownlow. "But a periodic eye exam is also necessary to assess the overall health of the eyes, to determine whether or not the patient needs vision correction with lenses or just to reassure you that all is fine."

According to Dr. Brownlow, the typical eye exam lasts about 30 minutes and begins with a case history, in which the doctor reviews the patient's medical background and asks about past vision problems.

After that, the doctor examines both the exterior and interior of the eye, looking for possible damage caused by disease, injury or aging. "With the help of modern instruments, we can look at the iris, then straight through the pupil all the way back to the retina."

Depth perception, peripheral vision, and the clarity and accuracy of vision at various distances also are tested. The doctor will prescribe corrective eyewear where appropriate.

Confidence in Your Eye care Doctor

How can patients be sure they are getting a high-quality eye exam? "I think the best way to judge that is to think about how you feel when it's over," says Dr. Brownlow. "Do you have a feeling of confidence in the doctor? Did he or she care enough to ask about your life and your health? Were tests performed skillfully and compassionately?

"You want to make sure that the doctor had a good, long look inside your eye. That process usually takes a couple of minutes -- and even though most of us don't like that bright light shining in our eyes, we should put up with it so that the doctor can do his or her job carefully and thoroughly.

"Sure, the technology continues to accelerate every year, and both optometrists and ophthalmologists are now equipped with more tools than ever before," says Dr. Brownlow. "But the foundation remains the caring human being behind the instrument, your doctor."

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